This is a research grant application (R01) to conduct a comprehensive, mixed-methods longitudinal survey of a cohort of same-sex and heterosexual couples to examine how legalized status, sexual orientation, gender, and other psychosocial variables affect relationship and individual well-being over time. Although there has been much progress made in reducing social and institutional discrimination against lesbian, gay, and bisexual people over the past two decades, same-sex couples are still unable to obtain legalized relationships in most areas of the United States. Of the few U.S. states to grant same-sex couples legal rights, Vermont was the first with civil union legislation in 2000. In 2002 we conducted a survey of same-sex couples who obtained a civil union in Vermont during the first year the legislation was available; we also surveyed matched comparisons of same-sex couples who did not obtain civil unions and heterosexual married couples. In 2005 we conducted a 3-year follow up study to examine the effects of legalization as well as predictors of relationship quality. The proposed grant is to conduct a comprehensive, mixed-methods follow-up study of all three types of couples in 2012. By surveying couples 10 years after the original study, we will be able to identify both cross- sectional and longitudinal factors that influence relationship and personal well-being for same- sex and heterosexual couples. Given that same-sex marriage is now available in 5 U.S. states and the District of Columbia, this study will also allow us to examine whether marriage is associated with greater well-being than other forms of legalization among same-sex couples. The proposed grant is a partnership between investigators at the University of Washington, San Diego State University, University of Kentucky, and Stony Brook University. The investigative team will conduct a two-phase study in which we will (1) conduct a comprehensive survey examining demographics, relationship factors, minority stress, and well- being among all three types of couples, and (2) conduct in-depth qualitative interviews with purposively selected couples and individuals from the larger sample. As the first comprehensive longitudinal study of legalized relationships among same-sex couples, the proposed study has important public health implications as it seeks to understand how public policies and other social and interpersonal factors can affect optimal adult development and functioning over time, especially in the area of intimate relationships and psychological well- being. This application reflects NICHD's goals to improve the health of women, men, and families and to learn about growth and development